Natural caloric sugars, such as sucrose, fructose and glucose, are utilized to provide a pleasant taste to beverages, foods, pharmaceuticals, and oral hygienic/cosmetic products. Sucrose, in particular, imparts a taste preferred by consumers. Although sucrose provides superior sweetness characteristics, it is caloric. Non-caloric or low caloric sweeteners have been introduced to satisfy consumer demand. However, sweeteners within this class differ from natural caloric sugars in ways that continue to frustrate consumers. On a taste basis, non-caloric or low caloric sweeteners exhibit a temporal profile, maximal response, flavor profile, mouth feel, and/or adaptation behavior that differ from sugar. Specifically, non-caloric or low caloric sweeteners exhibit delayed sweetness onset, lingering sweet aftertaste, bitter taste, metallic taste, astringent taste, cooling taste and/or licorice-like taste. On a source basis, many non-caloric or low caloric sweeteners are synthetic chemicals. The desire for a natural non-caloric or low caloric sweetener that tastes like sucrose remains high.
Stevia rebaudiana Bertoni is a perennial shrub of the Asteraceae (Compositae) family native to certain regions of South America. Its leaves have been traditionally used for hundreds of years in Paraguay and Brazil to sweeten local teas and medicines. The plant is commercially cultivated in Japan, Singapore, Taiwan, Malaysia, South Korea, China, Israel, India, Brazil, Australia and Paraguay.
The leaves of the plant contain a mixture containing diterpene glycosides in an amount ranging from about 10% to 20% of the total dry weight. These diterpene glycosides are about 150 to 450 times sweeter than sugar. Structurally, the diterpene glycosides are characterized by a single base, steviol, and differ by the presence of carbohydrate residues at positions C13 and C19. Typically, on a dry weight basis, the four major steviol glycosides found in the leaves of Stevia are dulcoside A (0.3%), rebaudioside C (0.6-1.0%), rebaudioside A (3.8%) and stevioside (9.1%). Other glycosides identified in Stevia extract include rebaudioside B, D, E, and F, steviolbioside and rubusoside. Among these, only stevioside and rebaudioside A are available on a commercial scale.
The use of steviol glycosides has been limited to date by certain undesirable taste properties, including licorice taste, bitterness, astringency, sweet aftertaste, bitter aftertaste, licorice aftertaste, and become more prominent with increase of concentration. These undesirable taste attributes are particularly prominent in carbonated beverages, where full replacement of sugar requires concentrations of steviol glycosides that exceed 500 mg/L. Use at that level results in significant deterioration in the final product taste.
Accordingly, there remains a need to develop natural reduced or non-caloric sweeteners that provide a temporal and flavor profile similar to that of sucrose.
There remains a further need for methods for purifying steviol glycosides from stevia. 